Gimsa J, Marszalek P, Loewe U, Tsong T Y
Department of Biochemistry, University of Minnesota College of Biological Sciences, St. Paul 55108.
Biophys J. 1991 Oct;60(4):749-60. doi: 10.1016/S0006-3495(91)82109-9.
Dielectrophoresis and electrorotation are commonly used to measure dielectric properties and membrane electrical parameters of biological cells. We have derived quantitative relationships for several critical points, defined in Fig. A 1, which characterize the dielectrophoretic spectrum and the electrorotational spectrum of a cell, based on the single-shell model (Pauly, H., and H.P. Schwan, 1959. Z. Naturforsch. 14b:125-131; Sauer, F.A. 1985. Interactions between Electromagnetic Field and Cells. A. Chiabrera, C. Nicolini, and H.P. Schwan, editors. Plenum Publishing Corp., New York. 181-202). To test these equations and to obtain membrane electrical parameters, a technique which allowed simultaneous measurements of the dielectrophoresis and the electrorotation of single cells in the same chamber, was developed and applied to the study of Neurospora slime and the Myeloma Tib9 cell line. Membrane electrical parameters were determined by the dependence of the first critical frequency of dielectrophoresis (fct1) and the first characteristic frequency of electrorotation (fc1) on the conductivity of the suspending medium. Membrane conductances of Neurospora slime and Myeloma also were found to be 500 and 380 S m-2, respectively. Several observations indicate that these cells are more complex than that described by the single-shell model. First, the membrane capacities from fct1 (0.81 x 10(-2) and 1.55 x 10(-2) F m-2 for neurospora slime and Myeloma, respectively) were at least twice those derived from fc1. Second, the electrorotation spectrum of Myeloma cells deviated from the single-shell like behavior. These discrepancies could be eliminated by adapting a three-shell model (Furhr, G., J. Gimsa, and R. Glaser. 1985. Stud. Biophys. 108:149-164). Apparently, there was more than one membrane relaxation process which could influence the lower frequency region of the beta-dispersion. fct1 of Myeloma in a medium of given external conductivity were found to be similar for most cells, but for some a dramatically increased fct1 was recorded. Model analysis suggested that a decrease in the cytoplasmatic conductivity due to a drastic ion loss in a cell could cause this increase in fct1. Model analysis also suggested that the electrorotation spectrum in the counter-field rotation range and fc1 would be more sensitive to conductivity changes of the cytoplasmic fluid and to the influence of internal membranes than would fct1, although the latter would be sensitive to changes in capacitance of the cytoplasmic membranes.
介电电泳和介电旋转常用于测量生物细胞的介电特性和膜电参数。我们基于单壳模型（保利，H.，和H.P.施万，1959年。《自然科学杂志》14b：125 - 131；索尔，F.A. 1985年。《电磁场与细胞之间的相互作用》。A.基亚布雷拉、C.尼科利尼和H.P.施万编辑。普伦纽姆出版公司，纽约。181 - 202），推导了图A1中定义的几个关键点的定量关系，这些关键点表征了细胞的介电电泳谱和介电旋转谱。为了检验这些方程并获得膜电参数，开发了一种允许在同一腔室中同时测量单个细胞的介电电泳和介电旋转的技术，并将其应用于对粗糙脉孢菌黏液和骨髓瘤Tib9细胞系的研究。膜电参数由介电电泳的第一个临界频率（fct1）和介电旋转的第一个特征频率（fc1）对悬浮介质电导率的依赖性来确定。粗糙脉孢菌黏液和骨髓瘤的膜电导分别也被发现为500和380 S m⁻²。一些观察结果表明，这些细胞比单壳模型所描述的更为复杂。首先，由fct1得出的膜电容（粗糙脉孢菌黏液和骨髓瘤分别为0.81×10⁻²和1.55×10⁻² F m⁻²）至少是由fc1得出的膜电容的两倍。其次，骨髓瘤细胞的介电旋转谱偏离了类似单壳的行为。通过采用三壳模型（富尔，G.，J.吉姆萨和R.格拉泽。1985年。《生物物理研究》108：149 - 164）可以消除这些差异。显然，存在不止一个膜弛豫过程会影响β - 色散的低频区域。发现在给定外部电导率的介质中，大多数骨髓瘤细胞的fct1相似，但对于一些细胞，记录到fct1显著增加。模型分析表明，细胞中由于离子大量损失导致的细胞质电导率降低可能会导致fct1的这种增加。模型分析还表明，在反向场旋转范围内的介电旋转谱和fc1对细胞质流体的电导率变化和内膜的影响将比fct1更敏感，尽管fct1对细胞质膜电容的变化敏感。
